The easiest to set up will be Keyclone.
Download it from www.solidice.com/keyclone
Extract to a folder of choice, run it, paypal for a license.
There are video's on his site showing easy set up.
It costs $20 or so, for a lifetime license.

I'm personally using that software, and chances are more people on this site use it then any other software option. As far as keyboard broadcasting goes, its as strong as any of the others. If you're interested in mouse broadcasting, it can do it, but I've been looking at Innerspace lately especially because of the the mouse broadcasting strength (targeting click on ground spells like Blizzard, Flame Strike, Hurricane etc).